That may be feasible here in North America, but in Sri Lanka an A/C unit might be a rather expensive luxury.

As opposed to an active liquid cooling system?

I'm talking about buying a portable AC unit to make this happen, as opposed to modifying the car's own AC to provide battery cooling. While we can run down to Home Depot or Costco and buy a Chinese-made window AC unit for around a hundred bucks, that may not be the case in other countries.

I'm talking about buying a portable AC unit to make this happen, as opposed to modifying the car's own AC to provide battery cooling. While we can run down to Home Depot or Costco and buy a Chinese-made window AC unit for around a hundred bucks, that may not be the case in other countries.

First, I'm talking about a portable A/C unit, not a window unit. They run about $400 here. A window unit would not work. Second, I'm guessing that someone who can afford a used Leaf in Sri Lanka an afford a portable A/C unit, even if only a used one. As for using the car's own A/C unit, that is likely possible, but even more likely to be very difficult and not exactly low-cost as well. But hey, whatever...

OK, looking at your post again, I'm definitely confused. I suggested using a portable A/C unit, and you seem to be suggesting that no, they need to buy a portable A/C unit, instead. What exactly do you want to do?

Thanks all for the replies! All your suggestions give me areas to think and issues of the methods I thought of. So please share them all!

Nubo wrote:Filling the case with fluid is an interesting concept. The first (really big) question is whether there's a fluid that could safely be introduced into the pack long-term. Second question is how much such a fluid would cost, and then there is weight. Finally, how fluid-tight is the case once it's filled with many pounds of liquid and subjected to G-forces.

Assuming all these work out, it probably help to conduct heat from the cell internals to the metal case (much better than air), where you could then extract it fairly easily in a number of ways.

Correct Nubo, these are good points to think about. Also will be the best option to bring out the heat from the battery modules.

LeftieBiker wrote:Given the risks and expense involved in liquid cooling, I'd first try one or two portable A/C units, with the cold air hose(es) blowing into the car's front or rear air channel(s).

Yes this is also possible. Then again issue comes with low heat carrying capacity of air compared to other coolant such as water/glycol. But its better to use some sort of cooling than without any cooling. LefiteBiker how much power does the portable a/c unit consumes?

knightmb wrote:

Nubo wrote:Filling the case with fluid is an interesting concept. The first (really big) question is whether there's a fluid that could safely be introduced into the pack long-term. Second question is how much such a fluid would cost, and then there is weight. Finally, how fluid-tight is the case once it's filled with many pounds of liquid and subjected to G-forces.

Assuming all these work out, it probably help to conduct heat from the cell internals to the metal case (much better than air), where you could then extract it fairly easily in a number of ways.

Take from those using liquid cooling for computer boards, it sounds cool but is not practical. First you need a liquid that is an electrical insulator (for obvious reasons electric car), and then you want something that won't corrode or mess up any internal wiring, battery, etc. The problem is, just about anything liquid is going to have some weird reaction with metal. Air just works better as being the least reactive. Add in what has mentioned, extra weight, sloshing, leaking, etc. It would be better to just vent filtered air through the battery pack given all it would take create the desired effect using liquid.

Knifhtmb yes, have you seen whole computers dipped in mineral oil for cooling. All the issues you mention are things we have to consider. How about if we can add ducts to the battery pack and circulate the air through a radiator like its done in intercoolers for turbocharged vehicles? also if we can mix cool air through a a/c system it will increase the cooling right? Getting the ducting to be fully water tight would be the challenge.

Evoforce wrote:I also have been considering some solutions but haven't yet put myself to full task of developing such a system. In our hot climate of Arizona USA, pushing hot air around a hot battery is meaningless. Also as previously mentioned, the car interior heats up when parked as well as parking over a hot surface.

A blowing fan may be slightly helpful in the interior of the car while parked and on the outside of the battery case but mostly not.

I have also considered a heat reflective addition or sticky to the plastic shield between the ground and the battery.

A belly shell to the battery outside case that could hold a cooling liquid. or A/C coolant lines and blower.

Plumbing existing A/C cooling in the cabin up the console channel between the seats to the hole in the floor forward/ahead of the back seats while either just blowing on the outer case or (better) going in through the the top of the case (watertight) and exhausting as high as possible in the engine compartment or body exterior at the rear as high as possible using anti backflow.

Also considered the direct liquid cooling of the pack with circulating pump and radiator using an appropriate oil that would not be corrosive or damaging to electronics or metals and other components.

The bad thing about using ambient air or liquids in a hot climate is they are also hot or become hot and less effective unless cooled by more than just airflow. I think the best way is going to involve refrigerant.

I have other thoughts but no time to write now...

Yes the cooling medium that used for battery cooling has to go below the ambient temperature when the ambient temp is high. That's why Tesla and other EV's couple the cooling fluid with their HVAC system to bring the temp down of the cooling fluid. But the down side is it will take considerable amount of power since it has to cool the coolant as well as cool the cabin(Nissan leaf takes roughly 2kW for cabin cooling). Please share your ideas when you are free.

Levenkay wrote:Here's kind of a gold-plated suggestion (in the sense of cost, not necessarily value): use a translacent heat pipe to move the battery's heat out to some external radiator. It would be way easier to keep the battery pack sealed that way, and I understand there are some clever ways to control the "thermal conductivity" of such an arrangement, which would let one switch the pack from an insulated condition for wintertime use, to a heatsunk condition for summer.

Yes Levenkay I also thought of that but the issue I faced was heat pipes has significantly less efficiency when transferring heat in horizontal direction, they are most efficient when they are placed in vertical direction.

I'm seriously thinking of investing some money to come up with a proper cooling mechanism.

I read most of the research papers done by NREL they have very valuable technical data on these areas Kudos to them I will share what I found in a future post!

Sorry if I missed anyone's post. Thanks again for taking time to reply to this post!

I'm talking about buying a portable AC unit to make this happen, as opposed to modifying the car's own AC to provide battery cooling. While we can run down to Home Depot or Costco and buy a Chinese-made window AC unit for around a hundred bucks, that may not be the case in other countries.

First, I'm talking about a portable A/C unit, not a window unit. They run about $400 here. A window unit would not work. Second, I'm guessing that someone who can afford a used Leaf in Sri Lanka an afford a portable A/C unit, even if only a used one. As for using the car's own A/C unit, that is likely possible, but even more likely to be very difficult and not exactly low-cost as well. But hey, whatever...

As I've learned from international travel (albeit not to Sri Lanka), something that costs $400 in the US could be considerably more expensive overseas. That was my point. But hey, it's just an idea I threw out there, no different than you throwing out an idea.

OK, looking at your post again, I'm definitely confused. I suggested using a portable A/C unit, and you seem to be suggesting that no, they need to buy a portable A/C unit, instead. What exactly do you want to do?

First, I don't want to do anything. It's not my car.

Second, I conflated "portable" with "window." To be honest, I don't see much of a difference in function between the two besides couple of hoses to further separate the cold and hot air outlets. We use these "portable" units at my work when the main A/C goes down, so that we can still keep our computers running, so I do know a bit about them.

And some smaller window units are indeed portable, or as portable as one can get with something like an air conditioner.

Such expensive project will not pay back. Filling battery with liquid is not technically reasonable. Battery will still be hot as outsidethat battery there is still no more heat extraction as before.Using water jacket around the battery is overkill. Coolant will still be at ambient and airinside the battery will be insulator (cells don't touch the casing).

If that is not enough next step is to cool the ambient temperature around the vehicle.Battery has massive heat capacity. 7 hours at night in garage that is 20C colder than outsideis possible. Massive insulation (or underground), very small garage (height no more than humanheight) etc.

That solution is power hungry. It is cheaper to buy new battery pack than preserve original packfor longer. Underground garage (passively cold) is the most reasonable (plus my DIY solution).If there is unlimited cold water available then that using a sprinkler might also work.

This entire idea seems like a waste of energy and money, not to mention the pack is designed to heat and cool uniformly. Unless a system is designed to do the same at the module level it is likely going to cause varying temps in the pack and uneven aging and lots of thermal imbalance.

You could use the solution that the Kea Soul EV uses, have air conditioned cabin air to cool the battery with a air vent from under the passenger seat go into the top of the battery case through a normally closed valve. The exhaust air could come out of the rear of the battery to be exhausted overboard.

The inlet would have a fan on it to get the air into the battery (our outlet, see KIA video https://www.youtube.com/watch?v=DoWRlH1bTuc , the normally closed valve would be activated by 12 volts so if the car turns off in an emergency the valve would close. The exhaust valve would have to have a backflow preventer to ensure if you drove through a pond the water wouldn't enter the battery.

Filling the battery with fluid would add considerable weight and you would have a unsecured load shifting around underneath you.

Yes, it is going to take cooler than ambient air but also, it needs to be cooled even when unattended in places such as Arizona etc. I had looked at the Kia system that is placed in and under the rear cargo area but that vehicle area in Arizona doesn't get that cool. But it is an improvement next to nothing. It takes a little time for the super heated cabin to cool down also. But for hotter climates (especially the summer) the leaf needs constant cooling for the chemistry that Nissan has produced thus far.

To someone that said that you would have unsecured shifting liquid weight, No, not if the cavity space was absolutely full. There is not sloshing in vessel that is totally full. More weight yes, and is putting liquid in the battery feasible? Maybe not, and is still a question based on what has been previously mentioned.